Applicator machine

ABSTRACT

An applicator machine and a process for heating and coating a section of pipeline. The applicator machine includes a frame configured to rotate about a section of pipeline to be heated and coated, rotating means operable to rotate the frame, and coating material applicators induction coils and radiant heaters mounted on the frame and rotatable therewith. The induction coil is configured to heat a section of pipeline adjacent to the induction coil to a coating material application temperature. The radiant heaters are configured to heat factory-applied coatings. Each coating material applicator sprays coating material through an aperture in a respective induction coil. The applicator includes an enclosure configured to surround a section of pipeline and provision for evacuating and collecting waste coating material. The coating material applicator may be configured to spray powder coating material, such as fusion bonded epoxy powder material and/or chemically modified polypropylene powder material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority, under 35 U.S.C. §119(a)-(d), to UKPatent Application No. GB 14 12 991.0 filed Jul. 22, 2014, the contentsof which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an applicator machine for heating andcoating a section of pipeline and a process for heating and coating asection of pipeline.

BACKGROUND OF THE INVENTION

Oil, gas and other pipelines are typically formed from multiple lengthsof individual steel pipe sections that are welded together end-to-end asthey are being laid. As used herein, a section of pipeline is any lengthof a pipeline construction whilst a pipe section is what is weldedtogether to form the pipeline construction. To prevent corrosion orother damage to the pipe sections occurring both from the environmentand during transportation, and to reduce heat loss of fluids transportedby pipelines, the pipe sections are coated with one or more protectiveand/or insulation layers. The pipe sections are usually externallycoated at a factory remote from the location in which they are to belaid. This is often referred to as factory-applied coating and it isgenerally more cost effective than coating pipe sections on site wherethey are laid. At the factory, the coating is applied to the outside ofthe pipe sections whereupon a short length of approximately 150 mm to250 mm is left uncoated at either end of the pipe section.

A coating may take several different forms depending on the particularcoating applicator. A conventional coating will typically comprise atleast a first, or ‘primer’, layer, such as a fusion bonded epoxy (FBE)material, that is applied in either liquid or powdered form to the outersurface of the steel pipe section while it is being heated. To ensure agood bond between the steel pipe section and the primer layer, the pipesection is typically blast cleaned and etched with an appropriate anchorpattern. The pipe section is heated by induction heating before theprimer layer is applied. The desired temperature would normally be thecuring temperature of the powdered or liquid primer material. On contactwith the heated pipe section surface the primer material coalesces andcures to form a continuous layer. The primer layer mainly protectsagainst corrosion. The primer layer may be used as the sole layer in acoating or it may be supplemented with a second layer to provideadditional mechanical protective and thermal insulation properties.

Polypropylene, polyethylene, and polyurethane material have goodmechanical protective and thermal insulation properties and they arecommonly used to coat pipelines transporting fluids at up to 140 degreesCelsius. Polypropylene, polyethylene and polyurethane are widely used infactory-applied coating for pipe sections. While curing of the primerlayer is ongoing, and so as to allow the layers to bond, a second layerof polypropylene, polyethylene or polyurethane coating is appliedcommonly by an injection moulding technique while the steel pipe sectionis heated by induction heating, for instance. All but the ends of thepipe section is enclosed by a heavy duty mould that defines a cavityaround the uncoated pipe section, which is subsequently filled withmolten polypropylene, polyethylene or polyurethane material from aninjection moulding machine in the factory. Once the second layer hascooled and solidified, the mould is removed to leave the factory-appliedcoating in place on the pipe section.

Optionally, if polypropylene is used as the second layer in the coating,an additional layer of chemically modified polypropylene (CMPP) materialwhich acts as an adhesive may be applied between the primer layer andsecond layer during the curing time (i.e. time taken to harden or set)of the primer layer. Likewise, if polyethylene is used as the secondlayer in the coating, an additional layer of polyethylene material whichacts as an adhesive may be applied between the primer layer and secondlayer during the curing time of the primer layer.

Optionally, the second layer may comprise polypropylene or polyethylenematerial in the form of a tape wrapped in a helix over the first primerlayer during the curing time of the primer. Optionally, the second layermay comprise a sleeve of polypropylene material heat-shrunk over thefirst primer layer during the curing time of the primer.

The uncoated ends are necessary to enable the pipe sections to be weldedtogether to form a pipeline in the field. A section of pipeline wherethe ends of adjacent pipe sections are joined by welding is known as afield joint. After welding, the exposed ends of the steel pipe sectionson either side of the weld (i.e. the field joint) must be coated. Fieldjoint coatings may be applied using techniques similar, or equivalent,to the factory-applied coating techniques. The field joint coatingshave, as far as is possible, the same mechanical and thermal propertiesas the factory-applied coatings by using compatible thermosettingplastics. Compatibility of the factory-applied and field joint coatingspermits fusion to occur between the factory-applied and the field jointcoatings, thereby imparting great integrity to the coatings at the fieldjoint section of pipeline. To assist with fusion, exposed chamfers atthe ends of the factory-applied coating on the pipe sections may bere-heated during the field joint operation.

Pipelines may be constructed in a dedicated facility where the pipelineis pulled through the facility in increments equal to the length of onepipe section, as is typical for offshore subsea pipelines. With thisconstruction process each welding, heating and/or coating operation isperformed in a fixed location with the field joint sections of pielinemoving into the position where the operations will be performed. Withthis construction process it is not always necessary to lift theequipment onto or off the pipeline.

Pipelines may be constructed in situ, where the pipe sections are weldedtogether and field-coated in, or very close to, the position in whichthe pipeline will be buried, as is typical for onshore cross-countrypipelines. With this construction process the equipment must betransported to each individual field joint in order to perform awelding, heating and/or coating operation to that section of pipeline.The equipment is continually lifted on and off the pipeline in order toperform the operations sequentially along the chain of field jointsections of pipeline.

Aside from the differences caused by the need to continually liftequipment for field coating on and off the pipeline, the welding,heating and/or coating features are similar to equipment for use in adedicated facility.

A known pipeline field joint coating applicator machine is disclosed,for example, in patent publication No. WO2009/024755. In this prior artpublication there is disclosed a two-frame system for mounting on apipeline whose field joints are to be coated with liquid or powderedcoating material. An induction coil encircles the first cylindricalframe and is moveable axially along the pipeline in order that selectedsections of pipeline (the field joints) may be heated to a temperatureat which the coating may adhere to the surface of the pipeline. Afterheating, the first frame is moved axially so that the heated filed jointsection of pipeline is then surrounded by the second cylindrical framewhich carries a rotatable coating material applicator. Rotation of theapplicator about the field joint applies coating material around thecircumference of that section of pipeline.

Another known pipeline field joint coating applicator machine isdisclosed, for example, in patent publication No. GB 2 181 396. In thisprior art publication there is disclosed an apparatus for preheating andcoating a section of pipeline comprising a cylindrical frame adapted toencircle and rotate about the section of pipeline in either direction, apair of arcuate heating sections mounted on the frame in spacedcircumferential relation with each other and a pair of single-nozzlecoating applicators mounted in spaced circumferential relation to eachother and between the heating sections. Each heater section comprises anarray of water-cooled tubes, each tube being arranged in a flat coilsandwiched between parallel plates to form a so-called ‘flat pack’. Theflat packs are separate elongate, longitudinally-orientated inductionheaters spaced around the section of pipeline above the surface thereofadjacent to, and parallel with, the surface of the pipeline. The coatingapplicators are for coating material on the surface of the section ofpipeline. The cylindrical frame is rotatable around the section of pipewhile simultaneously applying an alternating electric current to theinduction heaters to heat the section of pipeline to an applicationtemperature for the coating material. The coating material is appliedthereafter to the pre-heated section of pipeline through the materialapplicator while the cylindrical frame continues to rotate. The framecomprises an upper yoke section and two side yoke sections which pivotwith respect to the upper yoke section, and locking means for lockingthe two side yoke sections together at their bottoms to compete aclosure of the cylindrical frame about the pipeline.

A variety of equipment is available to coat sections of pipeline,largely aimed at reducing the time required to perform a coating processand economy of coating material, but also to help ensure a consistentapplication of coating material. For example, laying a pipelinetypically involves coating several thousand field joints thus, even asmall time saving in the time, or a small reduction in amount of coatingmaterial, required to coat each field joint can lead to significantoverall cost savings. Likewise, consistent application of coatingmaterial can lead to significant improvements in coating quality andlongevity.

BRIEF SUMMARY OF THE INVENTION

In an aspect of the present invention, there is provided an applicatormachine for heating and coating a section of pipeline, the applicatormachine comprising: a frame configured to rotate about a section ofpipeline to be heated and coated; rotating means operable to rotate theframe; a coating material applicator mounted on the frame and rotatabletherewith, and an induction coil mounted on the frame and rotatabletherewith, wherein the induction coil is configured to heat a section ofpipeline adjacent to the induction coil to a coating materialapplication temperature and wherein the coating material applicator isarranged to spray coating material through an aperture through theinduction coil.

With the applicator machine of the present invention, the pipeline neednot be moved between the operations of induction heating and coatingmaterial application of a section of pipeline. These two operations areperformed on the same small zone of the section of pipeline and theyrotate about the pipeline together with the frame. Thus, the cycle timefor operation of the applicator machine is diminished. Also, prior artapplicator machines tend to overheat the steel surface to compensate forheat decay in the time between induction heating and spray coating.Advantageously, the applicator machine of the present invention needonly heat the zone of the section of pipeline directly under theinduction coil to the minimum coating material application temperaturebecause the coating operation occurs simultaneously. In the field, thisavoids overheating a factory-applied coating on each side of field jointsection of pipeline being coated which may, because of human error,result in de-bonding of the factory-applied coatings which is highlyundesirable. In the field and in the factory, the induction coil needonly heat a shallow depth, or skin, of the section of pipeline ratherthan all of it. As a result, the steel of the section of pipeline heatsmore quickly and less energy is used. The applicator machine may be usedto heat and coat a section of a pipeline construction or a section of apipe section prior connection to a pipeline construction.

Preferably, the coating applicator is arranged to spray a strip ofcoating material. The strip of coating material may be arranged to makea broad sweep of coating material around the circumference of thesection of pipeline being heated and coated.

Preferably, the coating material applicator comprises a plurality ofspray nozzles arranged in an elongate row. This may provide a reliableand broadly even sweep of coating material as the frame rotates about asection of pipeline. This may help to avoid, as far as is possible, anyoverspray on the induction coil through which the coating material issprayed. However, as the skilled person will understand, the row ofspray nozzles is advantageous independently of whether the coatingmaterial spray passes through the middle of the induction coil.

Preferably, the nozzles are directed substantially orthogonal to theaxis of rotation of the frame. Thus, the angle of incidence of thecoating material spray with respect to the surface of the section ofpipeline may be zero. In other words, the coating material spray mayadopt a direct path to the section of pipeline.

Preferably, each nozzle comprises a flat slit arranged to spray coatingmaterial in a spray plane fanning out from the flat slit. The definedshape of a spray plane may facilitate neat strips of coating materialupon a section of pipeline. Preferably, the flat slit of each nozzle isrotatable. This may provide control over the shape and concentration ofthe coating material across the strip of coating material as it meetsthe section of pipeline. Rotation of the nozzles may enable calibrationand optimization of overlap between adjacent spray planes. This may helpto avoid uncontrolled turbulence or clusters of coating materialconcentrations where the spray meets the section of pipeline. In doingso, this may help to avoid undesirable coating material high/low pointson the section of pipeline being coated and achieve, as near aspossible, an uninterrupted smooth layer of coating material. Optionaladditional precision may be provided by flow regulators, one in linewhich each nozzle, to provide additional precision and control over theflow rate of coating material sprayed from the nozzles.

Preferably, the aperture through the induction coil is elongate in thedirection of the strip of coating material. The strip of coatingmaterial may be optimized to pass the maximum amount of coating materialthrough the aperture with the minimum of overspray on the inductioncoil.

Preferably, the induction coil is elongate with respect to the axis ofrotation of the frame. This may provide a reliable means of heating abroad sweep of the section of pipeline.

Preferably, the induction coil has a partially cylindrical undersidesubstantially coaxial with the axis of rotation of the frame. This maydirect and concentrate the induction heating effect towards the zone ofthe section of pipeline being heated and coated.

Preferably, the coating material applicator and the induction heaterform a heating and coating arrangement and wherein the applicatormachine comprises two heating and coating arrangements each beingmounted on substantially diametrically opposite sides of the axis ofrotation of the frame. This may increase heating and coating capabilityand save time.

Preferably, the machine comprises at least one radiant heaterarrangement disposed to heat factory-applied coatings. This may preparea field joint section of pipeline for another coating layer to be bondedwith the factory-applied coating in the next stage of the construction.

Preferably, each radiant heater arrangement is circumferentiallydisplaced about the axis of rotation of the frame from the or eachcoating material applicator and the or each induction heater. This mayavoid cluttering the frame and may evenly distribute weight about theaxis of rotation of the frame.

Preferably, the machine comprises an enclosure configured to surround asection of pipeline and means for evacuating and collecting wastecoating material. Coating material lost to the surrounding area, and notused to coat a section of pipeline, is a problem known as overspray. Theenclosure protects the section of pipeline from cross-winds and providesa calm internal environment which helps to alleviate the problem ofoverspray. The enclosure provides a means for collecting stray coatingmaterial for re-cycling it for the benefit of the environment.

Preferably, the coating material applicator is configured to spraypowder coating material, optionally fusion bonded epoxy powder materialand/or chemically modified polypropylene powder material.

In another aspect of the present invention, there is provided a processfor heating and coating a section of a pipeline, the process comprising:disposing a frame configured to rotate about a section of pipeline to beheated and coated; disposing an induction coil adjacent to the sectionof pipeline; directing a coating material applicator to spray coatingmaterial to the section of pipeline; rotating the frame, the inductioncoil and the coating material applicator as a unit around the section ofpipeline while simultaneously supplying alternating electrical power tothe induction coil to heat the section of pipeline; and spraying coatingmaterial through an aperture through the induction coil to the sectionof pipeline.

With the process of the present invention, the pipeline need not bemoved between the operations of induction heating and coating materialapplication of a section of pipeline. These two operations are performedon the same small zone of the section of pipeline as they rotate aboutthe pipeline with the frame. Thus, the cycle time for operation ofheating and coating material application is diminished. Also, prior artinduction heating and coating material application processes tend tooverheat the steel surface to compensate for heat decay in the timebetween induction heating and spray coating. Advantageously, the processof the present invention need only heat the zone of the section ofpipeline directly under the induction coil to the minimum coatingmaterial application temperature because the coating operation occurssimultaneously. In the field, this avoids overheating a factory-appliedcoating on each side of a field joint section of pipeline being coatedwhich may, because of human error, result in de-bonding of thefactory-applied coatings which is highly undesirable. In the field andin the factory, the induction coil need only heat a shallow depth, orskin, of the section of pipeline rather than all of it. As a result, thesteel of the section of pipeline heats more quickly and less energy isused. The process may be used to heat and coat a section of a pipelineconstruction or a section of a pipe section prior connection to apipeline construction.

Preferably, the process comprises directing the coating materialapplicator to spray a strip of coating material through an elongateaperture through the induction coil to the section of pipeline. Thestrip of coating material may be optimized to pass the maximum amount ofcoating material through the aperture with the minimum of overspray onthe induction coil.

Preferably, the coating material applicator sprays coating material witha plurality of spray nozzles arranged in an elongate row. This mayprovide a reliable means of producing a broad sweep of coating material.

Preferably, the nozzles spray coating material in a substantially radialdirection with respect to the section of pipeline. Thus, the angle ofincidence of the coating material spray with respect to the surface ofthe section of pipeline may be substantially zero. In other words, thecoating material spray may adopt a direct path to the section ofpipeline.

Preferably, the induction coil heats a partially cylindrical section ofpipeline elongate with respect to a longitudinal axis of the pipeline.This may direct and concentrate the induction heating effect towards thezone of the section of pipeline being heated and coated.

Preferably, the process comprises heating factory-applied coating of thesection of pipeline with a radiant heater arrangement disposed upon theframe. This may prepare a field joint section of pipeline for anothercoating layer to be bonded with the factory-applied coating in the nextstage of the construction.

Preferably, the process comprises evacuating and collecting wastecoating material from an enclosure surrounding the section of pipeline.Coating material lost to the surrounding area, and not used to coat asection of pipeline, is a problem known as overspray. The enclosureprotects the section of pipeline from cross-winds and provides a calminternal environment which helps to alleviate the problem of overspray.The enclosure provides a means for collecting stray coating material forre-cycling it for the benefit of the environment.

Preferably, the process comprises spraying powder coating material,optionally fusion bonded epoxy powder material and/or chemicallymodified polypropylene powder material.

In the description which follows reference is made to construction ofthe pipeline at a dedicated facility, where the pipeline moves into theposition where the welding and coating operations are performed.However, an applicator machine with a hinged cylindrical frame adaptedto be continually lifted on and off the pipeline and transported fromone field joint to the next is also referenced.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained, by way of example only,with reference to the accompanying drawings of which:

FIG. 1 shows a cross-sectional view of two joined pipe sections eachwith a factory coating;

FIG. 2 shows a perspective view of an embodiment of a coating machineaccording to the present invention;

FIG. 3 shows a side elevation view of the coating machine of FIG. 2;

FIG. 4 shows a cross-section IV-IV of the coating machine as it is shownin FIG. 3;

FIG. 5 shows a perspective view of the cross-section of FIG. 4;

FIG. 6 shows a perspective view of cylindrical frame of the coatingmachine;

FIG. 7 shows a top view of the cylindrical frame of FIG. 6;

FIG. 8 shows a detail VIII of a powder applicator on the cylindricalframe as it is shown in FIG. 7;

FIG. 9 shows a top view of the powder applicator in use on a field jointsection of pipeline;

FIG. 10 shows a cross-section X-X of the powder applicator as it isshown in FIG. 9;

FIG. 11 shows a detail XI of the powder applicator as its is shown inFIG. 9;

FIG. 12 shows a side elevation view of components of the powderapplicator in use on a field joint section of pipeline;

FIG. 13 shows a perspective view of components of FIG. 12 from one end;

FIG. 14 shows a perspective view of components of FIG. 12 from one sidein partial cross-section;

FIG. 15 shows a top view of an induction heater plate.

As mentioned above, multiple hollow cylindrical steel pipe sections arewelded together to construct a pipeline. The individual lengths of pipesections are, prior to being welded into a pipeline, normally coated ata factory remote from where the pipeline is laid.

Referring to FIG. 1, there are shown two steel pipe sections 40, 42joined together in end-to-end relation by a welded joint 44 to form whatis only a section of a pipeline which may extend over many kilometers.The pipe sections 40, 42 have the same central longitudinal axis A-A.Approximately, but not limited to, 150 mm to 250 mm of bare, typicallyblast cleaned, steel at the ends 46, 48 of the pipe sections 40, 42enables welding of the welded joint 44. The ends 46, 48 of the pipesections 40, 42 and the welded joint 44 are referred to as the fieldjoint. The rest of the pipe sections 40, 42 are coated with afactory-applied coating 50, 52 of polypropylene, polyethylene orpolyurethane. As mentioned above, the factory-applied techniquetypically comprises a first thin primer layer of FBE material. Thecylindrical portions 54, 56 of the factory-applied coating 50, 52 areprogressively cut back as conical chamfered portions 58, 60 in theapproach to the bare steel ends 46, 48 of the pipe sections 40, 42.

Referring to FIGS. 2 and 3, there is shown an applicator machine 100 forthe oil and gas pipeline industry according to the present invention.The applicator machine 100 comprises a generally cubic-shaped orcuboid-shaped enclosure 102. The enclosure 102 has in internal cavitythrough which may pass a pipeline. The enclosure 102 has a pair ofmutually aligned circular pipeline holes 104 a, 104 b, one through eachopposite end of the body and coaxial with a longitudinal axis A-Athrough the centre of the applicator machine 100. The pipeline holes 104a, 104 b are large enough to accommodate the passage of pipelines havingvarious diameters of anywhere between 0.05 meters to 1.5 meters.

The enclosure 100 has a lockable hinged door 106 a, 106 b on eachopposite side to provide an operator with access to inside the enclosure102. Each door 106 a, 106 b has a respective window 108 a, 108 bproviding an operator with visibility of inside the enclosure 102.

The bottom of the enclosure 102 is shaped as a hopper 110 to collect anystray powder coating material heavy enough to fall towards the hopper110, under gravity, and direct it towards a heavy powder extraction tube111 at a lowest point of the hopper 110. CMPP powder is relatively heavyand more likely to drop to into the hopper 110 than FBE powder.

The top of the enclosure 102 is has a light powder extraction port 112to suck out any stray powder coating material light enough to remainairborne and direct it towards a light powder extraction tube 113. FBEpowder is relatively light and more likely to remain airborne than CMPPpowder.

The heavy and light powder extraction tubes 111, 113 are connected, viaan air filter (not shown), to a vacuum pump (not shown) which drawspowder-entrained air from the enclosure 102. The purpose of the heavyand light powder extraction tubes 111, 113 is to evacuate powderedcoating material that has not adhered to the surface of the field joint44, 46, 48 from the enclosure 102 and pass it through the air filter,where it is separated from the air flow, and collect it in a bin (notshown) to be discarded later. Cleaned air flows downstream from thefilter to the vacuum pump where it is exhausted to atmosphere. The airfilter, collection bin and vacuum pump are standard parts well known inthis field of technology.

The applicator machine 100 comprises a CMPP fluid bed 114 for storingchemically modified polypropylene in powder form and a FBE fluid bed 116for storing fusion bonded epoxy in powder form. The CMPP fluid bed andthe FBE fluid bed are slidably accommodated in the applicator machine,adjacent to each other and under the hopper 110, to facilitate refillingas and when necessary.

At the bottom of each fluid bed 114, 116 is an air porous membrane (notshown) upon which sits FBE or CMPP powder material. An air pump (notshown) selectively pumps air though the membrane of one or both of thefluid beds 114, 116 thereby fluidizing the FBE or CMPP power materialcontained therein. FBE or CMPP powder-entrained air flows from theselected fluid bed(s) 114, 116 and passes through a venturi arrangement(not shown), which regulates the mix of powder and air in thepowder-entrained air flow. The powder-entrained air flows to a main feedpipe 150 to a pair of powder applicators 146, 148. The powderapplicators are discussed in more detail below. The air porousmembranes, air pump and venturi arrangement are standard parts wellknown in this field of technology.

The applicator machine 100 comprises a human/machine interface 118 toenable control of the applicator machine by an operator. The interface118 presents an operator with a menu to start or stop the applicatormachine 100 and/or select a coating process. Other aspects of thecoating process may be controlled automatically by the interface 118once the operator has started the applicator machine 100.

The enclosure 102 is supported on the ground by a base plate 120. Theapplicator machine 100 comprises an electric motor 122 fixed to theenclosure 102. The electrical power supply to the motor 122 iscontrolled by the interface 118.

Powdered FBE is widely used in the pipeline industry to protect steel.It is an anti-corrosion layer which is normally applied on bare metalwith a thickness of 200-500 microns to act as a primer layer or it canbe applied as the single layer coating with a thickness of a fewmillimeters.

Powdered CMPP is commonly used to the pipeline industry. It is anadhesive layer which is may be applied on the FBE primer layer with athickness of 400-800 microns. Optionally, CMPP powder may be mixed withFBE powder and sprayed upon a purely FBE primer layer (before a purelyCMPP layer is applied) in an interlock layer having a thickness of nomore than a couple of passes of the coating applicator. This interlocklayer is to improve bonding between the purely FBE primer layer and thepurely CMPP layer.

Referring to FIGS. 4 to 6, the applicator machine 100 comprises a frame124 circumscribing a generally cylindrical shape coaxial with the axisA-A of the pipeline holes 104 a, 104 b and a pipeline in the enclosure102. The frame is made of aluminium, stainless steel or anothersubstantially non-magnetic rigid material. The frame 124 is supportedfor rotation about the axis A-A by a pair of bearings 126 a, 126 b, oneat each opposite axial end of the body 112 adjacent a respectivepipeline hole 104 a, 104 b. The motor 122 is coupled to the frame 124via a transmission (not shown) protected by a shroud 127. Thetransmission may be any mechanism capable of transmitting the motor'srotational output to rotation of the frame, like, for example, anendless chain or belt or a drive shaft. The frame 124 is rotatable bythe motor 122 in both directions of double-headed arrow B through andarc of 180 degrees (+/−5 degrees to allow for coating overlap).Electrical power supply and operation of the motor 122 is controlled bythe interface 118.

The applicator machine 100 comprises two pairs of radiant heatercassettes 134 a, 134 a and 136 b, 136 b, each pair of radiant heatercassettes being fixed to diametrically opposite sides of the frame 124.The radiant heater cassettes 134 a, 134 a, 136 b, 136 b of each pair areaxially spaced from each other so that they may heat the chamferedportions 58, 60 of the factory-applied coatings 50, 52 of pipe sections40, 42 in the enclosure 102. One of each pair of radiant heatercassettes 134 a, 136 a heats one chamfered portion 58 while the other ofeach pair of radiant heaters cassettes 134 b, 136 b heats the otherchamfered portion 60. Electrical power supply and operation of theradiant heater cassettes 134 a, 134 b, 136 a, 136 b is controlled by theinterface 118.

The frame 130 comprises a pair of induction heater plates 138, 142, oneat each diametrically opposite side of the frame 124 approximatelyequidistant between the two pairs of radiant heater cassettes 134 a, 134a and 136 b, 136 b. Each induction heater plate 138, 142 has a partiallycylindrical underside 138 a, 142 a facing a field joint 44, 46, 48 inthe enclosure 102. The cylindrical undersides 138 a, 142 a arelongitudinally-orientated parallel to the axis A-A and match, as far aspossible, the cylindrical outer shape of a field joint 44, 46, 48. Thishelps the induction heater plates 138, 142 to direct and concentrate theinduction heating effect towards the field joint 44, 46, 48 section of apipeline to be heated and coated.

Referring to FIG. 15, there is shown the induction heater plate 138 inmore detail, it being understood that the other induction heater plate142 has the same basic construction. The induction heater plate 138 hasa generally rectangular outer profile 139, when viewed from above. Theinduction heater plate 138 is electrically coupled to a pair ofelectrical terminals 140 a, 140 b located at one end of the inductionheater plate 138. The outer profile 139 surrounds a rectangular centralaperture 141. The long sides of the outer profile 139 and the centralaperture 141 are arranged parallel to the axis A-A. One short side ofthe outer profile 139 is electrically split so that the induction heaterplate is effectively a single coil wherein one end of the coil iselectrically coupled to one terminal 140 a and the other end of the coilis electrically coupled to the other terminal 140 b. The terminals 140a, 140 b of each induction heater plate 138, 142 are connected to analternating electrical power supply (not shown) having, and purely forthe purpose of example, an output variable up to 110 kW and a frequencyof between 10 and 25 kHz to produce an induction heating effect in theinduction heater plates 138, 142. Alternating electrical power suppliesfor induction heaters are standard parts well known in this field oftechnology. Operation of the alternating electrical power supply to theinduction heater plates 138, 142 is controlled by the interface 118.

It is important that the induction heater plates 138, 142 areelectrically insulated from the structures they are mounted upon. Theinduction heater plates 138, 142 are coated or wrapped with aninsulating material.

Returning to FIGS. 4 to 6, the induction heater plates 138, 142 aresized and positioned so that they may heat the field joint 44, 46, 48section of pipeline (i.e. having an axial length of approximately 300 mmin the example shown, although it can be a length of 725 mm or more) upto, but not including, the chamfered portions 58, 60 of thefactory-applied coatings 50, 52.

The frame 130 comprises a pair of powder applicators 146, 148 one ateach diametrically opposite side of the frame 124. Each powderapplicator 146, 148 is arranged to apply a coating of FBE and/or CMPPpowder around the field joint 44, 46, 48. Operation of the powderapplicators 146, 148, is controlled by the interface 124.

Referring to FIGS. 6 to 14, there is shown the powder applicator 146 andthe induction heater plate 138 in more detail, it being understood thatthe other powder applicator 148 and the other induction heater plate 142has the same basic construction. The powder applicator 146 comprises amain feed pipe 150 fluidly connected to powder-entrained air flow fromthe CMPP powder bed 114 and the FBE powder bed 116 to the inlet of afeed pipe splitter 152. The feed pipe splitter 152 is supported on aplate 154 fixed to the frame 124. The power applicator 146 compriseseight split feed pipes 156 each fluidly connected from a respectiveoutlet of the feed pipe splitter 152 to the inlet of a respectivestraight nozzle feed 158.

The outlet of each of the array of eight nozzle feeds 158 comprises arotatable nozzle 160. In the example shown, there are eight sets of feedpipes 156, nozzle feeds 158 and nozzles 160 although there may be more,or fewer, depending on the type and dimensions of the section ofpipeline for which the applicator machine 100 is designed to coat. Eachnozzle feed 158 has a flow regulator to provide additional precision andcontrol over the flow rate of coating material sprayed from the nozzles160. Also, the flow regulators at the ends of the eight nozzle feedarray may be closed to alter the length of section of pipeline coated bythe applicator machine 100. The nozzle feeds 158 and the nozzles 160 aresupported by a bracket assembly 162 coupled a board 164 via a bracketcoupling mechanism 166.

The bracket coupling mechanism 166 comprises a pair of pillars 168 fixedto the top side of the board 164 and a pair of collars 170 fixed to thebracket assembly 162. Along the length of each respective pillar 168 isa line of equally-spaced notches 168 a. Each collar 170 surrounds arespective pillar 168. Each collar 170 has a retractable pin 170 anormally biased towards the notches 168 a of its pillar 168. An operatormay, prior to use of the applicator machine 100, pull both pins 170 aaway from the pillars 168 to disengage the pins 170 a from the notches168 a and to enable sliding movement of the bracket assembly 162 towardsor away from the board 164. When the operator ceases pulling, the pins170 a return towards their respective pillars 168 to engage whichevernotches 168 a are selected by the operator for the appropriate distancebetween the bracket assembly 162 and the board 164. The bracket assembly162 and the bracket coupling mechanisms 166 maintain the array of eightnozzles 160 in a straight line parallel to the axis A-A at a fixedlocation along the length of the axis A-A.

Each bracket assembly 162 comprises a respective pyrometer 171 formeasuring the surface temperature of the field joint 44, 46, 48 sectionof pipeline in its vicinity. These temperatures are communicated to theinterface 118 in real time. The interface 118 displays thesetemperatures to the operator.

The board 164 is coupled to the frame 124 via a pair of board couplingmechanisms 172, 174, one such board coupling mechanism being located ateach axial end of the board 164. The board coupling mechanisms 172, 174bias the board 164 a short radial distance towards the axis A-A. Theboard coupling mechanisms 172, 174 act independently of each other tomaintain the board 164 parallel to outer cylindrical shape of the fieldjoint 44, 46, 48 in the enclosure 102 which, in normal circumstances, isalso parallel to the axis A-A. The board coupling mechanisms 172, 174maintain the angle of incidence of the nozzles 160 with respect to thefield joint 44, 46, 48 as close as possible to zero degrees (i.e. aradial approach).

The board coupling mechanisms 172, 174 are connected to opposite axialends of the frame 124 by fasteners 173. Each fastener 173 engages arespective parallel row of notches 175, two of which are in each boardcoupling mechanisms 172, 174. Different notches 175 correspond todifferent distances of the board coupling mechanisms 172, 174 and theboard 164 from the axis A-A. Unfastening the fasteners 173 permitsselection of different notches 175. This, in turn, permits adjustment ofthe distance between the board 164 and the axis A-A to accommodatepipelines with different diameters.

The induction heater plate 138 is mechanically fixed to the bottom ofthe board 164 (on the opposite side to the bracket assembly 162). Asmentioned above, the induction heater plate 138 is electricallyinsulated from the board 164. The underside 138 a of the inductionheater plate 138 faces the field joint 44, 46, 48 in the enclosure 102.Also fixed to the bottom of the board 164 is a pair of rollers 176, 178,one at each opposite axial end of the board 164. The rollers 176, 178are rotatable about an axis parallel to the axis A-A. Each roller 176,178 is biased by a respective board coupling mechanism 172, 174 againsta respective factory-applied coating 50, 52 of pipe sections 40, 42 inthe enclosure 102. The rollers 176, 178 follow the shape of the pipesections 40, 42 and, in combination with the board coupling mechanisms172, 174, move the board 164 in a way that compensates for differentdiameters of pipe sections 40, 42 and/or deviations from a purelycylindrical outer shape. This tolerance ensures that the inductionheater plate 138 is maintained at about the right height (approximately10 mm to 20 mm) above the field joint 44, 46, 48 for optimum inductionheating and/or to avoid the welded joint 44 which can stand 5 mm proudof that section of pipeline.

Straight nozzle feeds 158 deliver a more laminar fluid flow to thenozzles 160 than would be delivered by curved nozzle feeds. As mentionedabove, powder-entrained air flow through the nozzles 160 is regulated bythe venturi arrangement upstream of the main feed pipe 150 for optimizedpowder coating thickness.

Referring in particular to FIGS. 10 to 12, each nozzle 160 comprises aflat slit which emits a spray plane 180 of powder-entrained air fanningout from the nozzle. The spray planes 180 have a generally fan-shapedprofile when viewed from above, as is shown in particular by FIG. 9. Thedistance d between adjacent nozzles 152 and an angle β subtended by thefan-shaped profile of the spray planes 180 are fixed. Distance D betweenthe nozzles 152 and the ends 46, 48 of pipe sections 40, 42 in theenclosure 102 is variable by adjustment of the bracket couplingmechanism 166 and/or the fasteners 173 in the board coupling mechanism172, 174.

Each nozzle 160 is adjustable to rotate in a clockwise CW, or acounter-clockwise CCW, direction about a central longitudinal axis ofits respective straight nozzle feed 158, as is shown in particular byFIG. 11. When viewing the nozzles end-on, the cross-sections of thespray planes 180 are arranged as an array of eight parallel lines eachinclined by a spray plane angle γ with respect to a central plane B-Bthrough the bracket assembly 162. The central plane B-B is substantiallyparallel to the axis A-A. The spray plane angle γ is adjustable, byrotation of the nozzles 160 between +90 degrees and −90 degrees, in themanner of a Venetian blind.

Each nozzle 160 has a respective collar with a tab 182 extendingradially away from the nozzle 160. Around each nozzle 160 is arespective arc of recesses 184 in the bracket assembly 162. Each tab 182has a detent 186. Inherent elasticity in the material of the tab 182biases the detents 186 into engagement with a recess 184. Each recess184 corresponds to a different spray plane angle γ for its adjacentnozzle 152. An operator can rotate the detents 186 between recesses 184to incrementally adjust the spray plane angle γ of the nozzles 160.

Adjustment of the distance D varies the point at which the spray planes180 meet the ends 46, 48 of pipe sections 40, 42 in the enclosure 102.Adjustment of the flow regulators of the nozzles feeds 158 varies theflow rate of coating material sprayed from the nozzles 160. Adjustmentof the spray plane angle γ varies the concentration and distribution ofpowder spray along the field joint 44 46, 48 at that meeting point. Thegreater the spray plane angle γ (up to +/−90 degrees) the further thatedges of adjacent spray planes 180 are from each other. Conversely, thesmaller the spray plane angle γ (down to zero degrees) the closer thatedges of adjacent spray planes 180 are to each other. It would beundesirable for adjacent spray planes 180 to overlap in a way thatcauses uncontrolled turbulence or clusters of powder concentrationsalong the array of nozzles 160. This could cause undesirable coatinghigh/low points on the field joint 44, 46, 48. Thus, before operation ofthe applicator machine 100, the operator configures the powderapplicators 146, 148, by alteration of one or more of the distance D,the position of the flow regulators, and the spray plane angle γ, sothat the nozzles 160 spray, as near as possible, an uninterrupted smoothlayer of powder over the field joint 44, 46, 48 section of pipeline.

Referring in particular to FIG. 14, each board 164 has an elongatecentral aperture 165 approximately the same size as, and locateddirectly above, the central aperture 141 through the adjacent inductionheater plate 138, 142. The array of eight spray planes 180 of the powderapplicator 146 is directed to pass through the central aperture 165 ofthe board 164 and the central aperture 141 of the induction heater plate138 to the field joint 44, 46, 48. Although not shown in FIG. 14, it isclear from the other figures that the array of eight spray planes 180 ofthe powder applicator 148 is likewise directed to pass through thecentral aperture 165 of its board 164 and the central aperture 141 ofthe induction heater plate 142 to the field joint 44, 46, 48. Asmentioned above, the spray planes 180 make a directly radial approach tothe field joint 44, 46, 48. Each powder applicator 146, 148 andinduction heater plate 138, 142 combination is arranged (in a radialplane containing the axis A-A) directly above a field joint 44, 46, 48section of pipeline. The spray planes 180 engage the pipe sections 40,42 under the induction heater plates 138, 142 precisely in the zone ofwhere induction heating of the pipe sections is optimized. This avoidsany heat decay between heating the skin of the steel pipe section 40, 42and applying the powder coating.

Operation of the applicator machine 100 shall now be described, withreference to FIGS. 1 to 14.

The welded joint 44 of two factory-coated pipe sections 42, 44 is fedthrough the pipeline holes 104 a, 104 b of the applicator machine 100 tothe middle of the frame 124. This can be visually checked by an operatorlooking though the windows 108 a, 108 b. The weight of the pipe sections42, 44 is supported on each side of the enclosure 102 by externalsupports (not shown). The enclosure 102 surrounds the field joint 44,46, 48 section of pipeline without performing a support function.

The operator selects a heating and coating process from the menupresented by the human/machine interface 118 and starts the applicatormachine 100.

The rollers 176, 178 contact the factory-applied coatings 50, 52 of pipesections 40, 42. The diametrically opposed induction heater plates 138,142 are activated before any spray coating starts. Heating isautomatically tuned by the alternating electrical power supply accordingto the distance between the induction heater plates 138, 142 and thebare steel field joint 44, 46, 48. The induction heater plates 138, 142are configured to heat the field joint 44, 46, 48 section of pipelinebetween the chamfered portions 58, 60 of the factory-applied coatings50, 52. The induction heater plates 138, 142 need only heat the surfaceof the field joint 44, 46, 48 to a depth of about 0.3 mm to the pre-setminimum FBE powder application temperature of 233 degrees Celsius +/−15degrees Celsius.

The pyrometers 171 are activated to monitor the surface temperature ofthe field joint 44, 46, 48 section of pipeline.

The electric motor 122 is activated to rotate the cylindrical frame 124,and all components mounted thereto, about the axis A-A in oscillatingsweeps of 180 degrees (or slightly more to avoid gaps in the arcs ofcoating material) in both directions of double-headed arrow B. Theinduction heater plates 138, 142 begin to heat the field joint 44, 46,48.

Once the surface temperature of the field joint 44, 46, 48 has reachedthe minimum FBE powder application temperature then the alternatingelectrical power supply changes to a lower power output to maintain thefield joint 44, 46, 48 ‘simmering’ at the minimum FBE powder applicationtemperature. The simmering is controlled by the interface 118. Heatingthe field joint 44, 46, 48 helps the CMPP powder and/or FBE powder toadhere to the surface.

If FBE powder coating is required then FBE powder-entrained air flowsfrom the FBE Fluid bed 116 to the powder applicators 146, 148 whichspray the heated field joint 44, 46, 48 with multiple passes of FBEpowder in a pre-defined application sequence.

Once the FBE powder coating has been applied, if a CMPP powder coatingis required air flow is switched from the FBE fluid bed 116 to the CMPPfluid bed 114. CMPP powder-entrained air flows from the CMPP fluid bed114 to the powder applicators 146, 148 which spray the heated fieldjoint 44, 46, 48 with multiple passes of CMPP powder in a pre-definedapplication sequence.

As an optional additional step, a thin combined FBE powder and CMPPpowder interlock layer may also be applied with a pre-definedapplication sequence where required. This consists of no more than acouple of passes of combined FBE powder and CMPP powder. To do this, airflow passes through both the FBE fluid bed 116 and the CMPP fluid bed114 at the same time.

Any stray FBE and/or CMPP powder particles, which have not adhered tothe heated field joint 44, 46, 48 during the coating process, arecontinually extracted from the enclosure 102 by suction through theextraction tubes 111, 113.

The two pairs of diametrically opposed radiant heaters 134 a, 134 b and136 a, 136 b may be activated, if necessary, before spray coating ends.The radiant heaters 134 a, 136 a are configured to heat one chamferedportion 58 of the factory-applied coating 50 and the radiant heaters 134b, 136 b are configured to heat the chamfered portion 60 of the otherfactory-applied coating 52. The purpose of this is to prepare thechamfered portions 58, 60 for bonding with a second layer of material tocompletely coat the field joint 44, 46, 48.

When the primer layer coating process is complete the radiant heaters134 a, 134 b and 136 a, 136 b and the induction heater plates 138, 142may remain active to keep the field joint 44, 46, 48 with newly-coatedprimer layer and the factory-applied coatings 50, 52 warm in preparationfor the next stage in the construction process where a second layer ofpolypropylene, polyethylene, and polyurethane material may be appliedover the primer layer to complete the field joint section of pipeline.

When the pipeline is ready, the field joint 44, 46, 48 with newly-coatedprimer layer is fed out of the applicator machine 100 which is ready toreceive the next section of pipeline to be coated with a primer layer.During this feeding process, the radiant heaters 134 a, 134 b and 136 a,136 b and the induction heater plates 138, 142 are deactivated.

Advantageously, there is no manual handling of the pipe sections 42, 44between the operations of (i) heating with the induction heater plates138, 142; (ii) coating with the powder applicators 146, 148; and (iii)heating with the radiant heater cassettes 134 a, 134 b and 136 a, 136 b.Thus, the cycle time for operation of the applicator machine 100 isdiminished.

Previous applicator machines tended to overheat the section of pipelineto compensate for heat decay in the time between induction heating andpowder spray coating. Advantageously, the applicator machine 100 onlyheats the field joint 44, 46, 48 section of pipeline to the minimumpowder application temperature because the powder coating process occurssimultaneously. This avoids overheating the adjacent factory-appliedcoatings 50, 52 which can, as a result of human error, result indis-bonding of the factory-applied coatings which is highly undesirable.Also, the induction heater plates 138, 142 only heat a 0.3 mm skin ofthe field joint rather than all of it. The steel heats more quickly. Theapplicator machine 100 makes more economical use of energy.

1. An applicator machine for heating and coating a section of pipeline,the applicator machine comprising: a frame configured to rotate about asection of pipeline to be heated and coated; rotating means operable torotate the frame; a coating material applicator mounted on the frame androtatable therewith, and an induction coil mounted on the frame androtatable therewith, wherein the induction coil is configured to heat asection of pipeline adjacent to the induction coil to a coating materialapplication temperature and wherein the coating material applicator isarranged to spray coating material through an aperture through theinduction coil.
 2. The applicator machine of claim 1, wherein thecoating applicator is arranged to spray a strip of coating material. 3.The applicator machine of claim 2, wherein the coating materialapplicator comprises a plurality of spray nozzles arranged in anelongate row.
 4. The applicator machine of claim 3, wherein the nozzlesare directed substantially orthogonal to the axis of rotation of theframe.
 5. The applicator machine of claim 3, wherein each nozzlecomprises a flat slit arranged to spray coating material in a sprayplane fanning out from the flat slit.
 6. The applicator machine of claim5, wherein the flat slit of each nozzle is rotatable.
 7. The applicatormachine of claim 2, wherein the aperture through the induction coil iselongate in the direction of the strip of coating material.
 8. Theapplicator machine of claim 2, wherein the induction coil is elongatewith respect to the axis of rotation of the frame.
 9. The applicatormachine of claim 1, wherein the induction coil has a partiallycylindrical underside substantially coaxial with the axis of rotation ofthe frame.
 10. The applicator machine of claim 1, wherein the coatingmaterial applicator and the induction heater form a heating and coatingarrangement and wherein the applicator machine comprises two heating andcoating arrangements each being mounted on substantially diametricallyopposite sides of the axis of rotation of the frame.
 11. The applicatormachine of claim 1, wherein the machine comprises at least one radiantheater arrangement disposed to heat factory-applied coatings.
 12. Theapplicator machine of claim 11, wherein the or each radiant heaterarrangement is circumferentially displaced about the axis of rotation ofthe frame from the or each coating material applicator and the or eachinduction heater.
 13. The applicator machine of claim 1, wherein themachine comprises: an enclosure configured to surround a section ofpipeline; and means for evacuating and collecting waste coatingmaterial.
 14. The applicator machine of claim 1, wherein the coatingmaterial applicator is configured to spray powder coating material,optionally fusion bonded epoxy powder material and/or chemicallymodified polypropylene powder material.
 15. A process for heating andcoating a section of a pipeline, the process comprising: disposing aframe configured to rotate about a section of pipeline to be heated andcoated; disposing an induction coil adjacent to the section of pipeline;directing a coating material applicator to spray coating material to thesection of pipeline; rotating the frame, the induction coil and thecoating material applicator as a unit around the section of pipelinewhile simultaneously supplying alternating electrical power to theinduction coil to heat the section of pipeline; and spraying coatingmaterial through an aperture through the induction coil to the sectionof pipeline.
 16. The process of claim 15, wherein the process comprisesdirecting the coating material applicator to spray a strip of coatingmaterial through an elongate aperture through the induction coil to thesection of pipeline.
 17. The process of claim 16, wherein the coatingmaterial applicator sprays coating material with a plurality of spraynozzles arranged in an elongate row.
 18. The process of claim 17,wherein the nozzles spray coating material in a substantially radialdirection with respect to the section of pipeline.
 19. The process ofclaim 15, wherein the induction coil heats a partially cylindricalsection of pipeline elongate with respect to a longitudinal axis of thepipeline.
 20. The process of claim 15, wherein the process comprisesheating factory-applied coating of the section of pipeline with aradiant heater arrangement disposed upon the frame.
 21. The process ofclaim 15, wherein the process comprises evacuating and collecting wastecoating material from an enclosure surrounding the section of pipeline.22. The process of claim 15, wherein the process comprises sprayingpowder coating material, optionally fusion bonded epoxy powder materialand/or chemically modified polypropylene powder material.